The full range amp which they no longer make had a freq resp from 5hz to 30khx

The new wide range amp they they sell has a freq resp from 6hz to 8 khz

I have spoken to several dealers who have damaged nice tower speakers with the new amp....best be used for sub application now.

Murphy,
The dealers you spoke with are giving you some very bad information. There is no increased risk when using this amplifier with fullrange speakers. The top end roll-off is caused by the inductors used on the final stage of the output section used to filter out the analog switching frequency which is many times beyond the audio bandwidth. All fullrange Class D amplifiers use these filter inductors. Even many triple darlington Class AB amplifiers use a similar inductor in the final output stage.
The JL Audio HD1200/1 has a more limited bandwidth than the recently revised HD750/1 although the HD750/1 retains the same bandwidth rating as the HD1200/1. Many so-called Class D amplifiers and triple darlington Class AB amplifiers have a similar top end range but you are not aware of it and you can't hear it....other than the placebo effect. The difference is the position held by JL Audio and their very conservative approach. If some off-the-wall product stretches their specs, no one cares. On the other hand, if someone tests a JL Audio product, even if out of context, and it doesn't exceed all JL Audio specs then it would be a major issue receiving major criticism. So, in this case, JL Audio has been extra conservative.
We tested the latest version of the HD750/1. Very simple test. Measure the output voltage at various frequencies at the same gain. Convert voltage to decibles. It is down a couple of dB at 20 kHz into a 4-ohm load with a slightly more aggressive roll-off into a 2-ohm load. You can't hear 20 kHz in a perfect quiet room let alone outside....no way. Plus, there is no way a 1.5" to 2" tweeter diaphram that is loaded into a compression chamber (typical HLCD) is going to reproduce 20 kHz....no way.
The risk to speakers comes from the fact that this is a very powerful amplifier and beyond the continuous thermal capacity of the speakers it is being used with.
Earmark uses an HD750/1 on each Rev410 plus an HD750/1 on each Rev10 on display. It is so loud it will make you cringe on rimshots and really dynamic passages, but it is always warm and clean, and they have never burned a display speaker to date.